Hi,

I'm using hibernate 3 and I have a table which contains nodes of a tree I want to display on the screen. I need to pass the tree data to my app as an XML document.

My hibernate mapping file for this table is shown at the end of the email.

I can get the hibernate code working fine to save and retrieve nodes and even access their children. My question is this - If I want to pull back a complete set of rows (maybe filtered and sorted by name) and build the xml to represent the tree, what is the most efficient strategy for this. I have read Hibernate in Action and seen some strategies regarding lazy loading and fetch depth but presumably at some point I may go beyond this depth and end up pulling back proxies.

Can anyone point me at a good article on saving and retrieving tree structures (it doesn't necessarily need to involve hibernate I guess). I've looked around but can't seem to find anything relevant.

Many thanks,
David

?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.accipia.centerview.model">
<class name="Objective" table="objectives">
<id name="id" type="long">
<column name="id" />
<generator class="native" />
</id>
<property name="shortName" type="string">
<column name="short_name" length="50" />
</property>
<property name="longName" type="string">
<column name="long_name" />
</property>
<property name="version" type="long">
<column name="version" />
</property>
<property name="description" type="string">
<column name="description" length="65535" />
</property>

<many-to-one
name="parent"
class="Objective"
column="parent_id"
cascade="none"/>

<set
name="children"
table="objectives"
cascade="save-update"
inverse="true">
<key column="parent_id"/>
<one-to-many class="Objective" />
</set>
</class>
</hibernate-mapping>

Hi,

for saving, I am using a simple Pojo:


For retrieving the data I'm mostly writing a selectable recursive stored procedure which reads the values from the tree and sorts them in a more "displayable" kind with a level and a position field. With XML I would display them with the tag names in the first field and the value of the field in the second etc. fields.

Chris